Impedance measurement systems can be used to determine the actual impedance of a signal path when the signal path has an impedance that depends on external conditions. In other words: when the signal path has a variable load impedance. In the case of mobile communication devices, the variable load impedance can be an antenna in a changing environment.
The transmission coefficient for transferred power can be optimized by tuning the signal line's impedance based on impedance information provided by an impedance measurement system.
Convention impedance measurement systems, e.g. known from U.S. Pat. No. 6,822,433, use two RSSI-chains to measure the levels of two signals. An additional conventional phase detector is needed to measure the phase between the two signals.
It is an object of the present invention to provide a phase detector that allows improved impedance measurement systems.
On that account, a phase detector according to independent claim 1 is provided. Dependent claims provide preferred embodiments of the invention.